CEDAR: Modeling Studies of Infrasonic Waves from Thunderstorms and Aurora

CEDAR：雷暴和极光次声波的建模研究

• 批准号: 0836391
• 负责人: Victor Pasko
• 金额: $ 25.35万
• 依托单位: Pennsylvania State Univ University Park
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-01-01 至 2013-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0836391&HistoricalAwards=false
• 关键词: CEDAR; Modeling; Studies; Infrasonic; Waves

This project is a three year effort to theoretically investigate mechanisms and effects of infrasonic waves generated by thunderstorms and aurora. The infrasonic waves correspond to acoustic waves in the frequency range 0.02-10 Hz. There is strong experimental evidence that thunderstorms and aurora represent significant sources of infrasonic wave activity spanning a broad altitude range from the troposphere up to the thermosphere. This evidence includes electrostatic production of 0.1-1 Hz infrasonic waves from thunderstorms, recent discovery of infrasound from lightning induced transient luminous events in the mesosphere called sprites, and radiation of infrasonic waves from supersonic auroral arcs and pulsating aurora. The project aims to characterize and quantify the observed infrasonic signals by undertaking a focused two-dimensional numerical modeling effort. It will address a limited set of unsolved problems related to infrasonic wave production by thunderstorms and aurora. The outstanding scientific questions to be pursued are: (1) What is the mechanism for the compression and rarefaction infrasonic pulses with periods 0.5 to 1 sec produced in association with lightning discharges? What is the fate and predicted signature of these pulses as they propagate downward and upward from thunderclouds and reach a remote observer after reflections from the ground and thermosphere? (2) What is the mechanism of the recently discovered infrasound radiation from sprites? Which physical factors, including both infrasound generation and propagation factors, contribute to formation of the chirp-like signatures that are observed? What are the specific features of observed waveforms, which would allow a remote observer to discriminate between infrasound radiation coming from thunderclouds at low altitudes and those from sprites? (3) What is the temporal and spatial structure of the body force acting on neutral air in auroral arcs that move with supersonic speeds, leading to auroral infrasound waves observed on the ground? What is the mechanism of the recently observed infrasound signals from pulsating aurora? Specific activities include development of a new efficient two-dimensional model of infrasound propagation using finite-difference time-domain techniques. The new model will be fully non-linear and will account for realistic temperature and wind structure in the Earth's atmosphere as well as for altitude dependent dissipation effects. The model will follow the fate of infrasonic wave packets at they propagate, reflect, and dissipate in the atmosphere in order to interpret existing published observations and to make specific predictions for future observations.

该项目是三年的努力，理论上研究了雷暴和极光产生的基外波的机制和影响。 频波对应于0.02-10 Hz频率范围内的声波。 有强有力的实验证据表明，雷暴和极光代表了跨越高度范围从对流层到热圈的广泛海拔范围的重要来源。 该证据包括来自雷暴的静电产生0.1-1 Hz的插射波，最近发现的闪电诱导的瞬态发光事件在称为Sprites的瞬时发光事件，以及来自超音速极光弧和脉动脉搏的插射波的辐射。 该项目的目的是通过进行集中的二维数值建模工作来表征和量化观察到的不传动信号。 它将解决与雷暴和Aurora相关的一组未解决的问题。 要提出的杰出科学问题是：（1）与闪电放电相关的0.5至1秒的压缩和稀疏式脉冲脉冲的机制是什么？ 当这些脉冲从雷云向下传播并在地面和热圈反射后到达遥远的观察者时，这些脉冲的命运和预测的签名是什么？ （2）最近发现的来自Sprites的伸展辐射的机制是什么？ 哪些物理因素，包括伸展产生和传播因素，有助于形成观察到的类似chirp的特征？ 观察到的波形的特定特征是什么，这将使远程观察者能够区分来自低海拔的雷云和Sprites的触发辐射？ （3）体力的时间和空间结构是用超音速速度移动的极光弧上中性空气的，导致地面上观察到的极光插射波？ 最近观察到的来自脉动极光的插射信号的机制是什么？ 特定的活动包括使用有限差分时间域技术开发新的有效的临时传播二维模型。 新模型将是完全非线性的，并将解释地球大气中的逼真的温度和风结构以及依赖高度的耗散效应。 该模型将遵循其传播，反映和消散的室内波波数据包的命运，以解释现有的已发表观测值并为将来的观察做出具体的预测。